In the case of gas discharge lamps such as fluorescent tubes, for example, AC current is conducted through a gas filling by means of two electrodes and thus excited to effect light emission. A voltage dropped across the gas discharge lamp during operation can increase on account of wear phenomena. This can take place uniformly in both current directions or else non-uniformly for both current directions, such that a rectifier effect occurs.
This increased voltage drop during the operation of the gas discharge lamp can lead to an increased power consumption and to greater heating of the gas discharge lamp. Particularly in the case of gas discharge lamps with a narrow glass bulb, that is at only a small distance from the electrodes, this excessive heating can lead to damage or else destruction of the gas discharge lamp.
It is an object to provide a method and also an apparatus for monitoring the operation of a gas discharge lamp by means of which a symmetrical and asymmetrical increase in the running voltage can be determined independently of one another in a simple manner.
This object is achieved according to the invention by means of a method having the features of Claim 1 and also an apparatus having the features of Claim 5. The subclaims describe in each case advantageous embodiments of the invention.